42 Of Flies . 
ing light bodies to fufpend and fallen themfelves to a!moil 
any furface. This will not feem ftrange, if we confl- 
der firft how fmall their bulk is when compared to their 
fuperficies, their thicknefs frequently not amounting to 
the looth part of an inch. Secondly, their ftrength and 
agility, compared to their bulk, which in that propor¬ 
tion perhaps may be an hundred times ftronger than an 
borfe. Thirdly, if we confider that nature always appro¬ 
priates the inftruments in the moft fit, eafy, and fim- 
pie manner poffible to perform their office; which is 
aIfo verified in the foot of a loufe, each of his legs 
being footed with two fmall daws, with which it grafps 
and thereby moves itfelf to and fro upon the hairs of 
the creature it inhabits. 
The legs of flies are bell applied to the microlcops, 
by being either ftuck upon the point, or held between 
the nippers. Though we frequently place them be¬ 
tween two talcs in an ivory Aider. 
Of the eyes and head of a grey drone fly. 
T HE llrudure of the eye in all creatures, is an 
admirable piece of mechanifm 3 but the beautiful 
contrivance of the eyes of infeds is fo peculiar, that 
it muft excite our admiration 3 fo fenced with its own 
hardnefs, that its own accurate vifion is a good guard 
againft external injuries 3 its outward coat being all over 
befet with curious lenticular inlets 3 enabling thofe crea¬ 
tures to fee very accurately every way, without any in¬ 
terval of time, or trouble to move the eye towards ob- 
jeds d . 
See fig. 83. This fly was made choice of, becaufe the 
inquiry being chiefly about the eyes, it was found to 
have 
f Derhanrs Phy, Theo. p. 171. 
